He said then-candidate Barack Obama could be elected because he was, "light-skinned" and had no "negro dialect."
Reid has apologized, and the president has accepted.
However, Sunday, some top Republicans called for Reid to resign, and it might be just the first of many surprises from the provocative new book.
The book pulls back the curtain on the battles not just between campaigns but also between running mates.
"How many times is Biden going to say something stupid?" Obama reportedly said after his vice presidential candidate's famous comment at a fundraiser:
"Mark my words," Biden said. "It will not be six months before the world tests Barack Obama like they did John Kennedy."
Obama's staffers say it "was as angry as they had ever seen" him.
About the campaign, former president Bill Clinton reportedly said, "Give me a break. This whole thing is the biggest fairy tale I've ever seen."
Clinton was even more dismissive of Obama in private with Sen. Ted Kennedy, according to the book.
"A few years ago, this guy would have been getting us coffee," Clinton reportedly said.
Worried about her husband, Hillary Clinton created a war room, the book claims, with staffers poised to deal with "a serious extramarital affair" by the former president.
When offered the job of secretary of state, Hillary Clinton balked, and she worried about her husband.
"You know I can't control him, and at some point he'll be a problem," she reportedly told the president-elect.
The book also indicates that the day after John Edwards' affair was alleged in the National Enquirer, Elizabeth Edwards, described by staff as condescending and intrusive, got so mad she ripped her blouse in an airport...exposing herself...telling her husband, "Look at me...."
John McCain's choice of Sarah Palin as a running mate was called "reckless" by Dick Cheney.
McCain staff worried too, holding talks on whether she was fit for office if the Republicans won.
"Can I call you Joe?" Palin asked of Biden at a campaign debate.
She asked that question because in debate preparations she repeatedly called her opponent 'O'Biden' instead of Biden. Staff members thought 'Joe' was safer.
After Palin's second television network interview, the book says she expressed regret for taking the vice presidential nomination:
"If I'd known everything I know now, I would not have done this," she reportedly said.
The authors say they have some transcripts and talked to 200 people. Some quotes in the book are direct while others are paraphrased statements.
Only a Palin spokesperson offered a comment Sunday, calling the descriptions "inaccurate."